In the hunt to determine what caused the fire that consumed Lahaina, the focus has increasingly turned to Hawaii’s biggest power utility — and whether the company did enough to prevent a wildfire in the high winds that swept over Maui last week.

Lawyers for Lahaina residents suing the utility, Hawaiian Electric, contend that its power equipment was not strong enough to withstand strong winds, and that the company should have shut down power before the winds came. Wildfire experts who have studied the catastrophic fires in California over the past two decades also see shortcomings in Hawaiian Electric’s actions.

Nearly a week after the wildfire tore through the island town of Lahaina, state and local officials have not determined a cause for the blaze that killed at least 99 people. But the explosive conditions were similar to those elsewhere in the country where wildfires were sparked by electrical equipment: dry brush, high winds and aging infrastructure.

Many wildfires in the United States occur when poles owned by utilities or other structures carrying power lines are blown down, or when branches or other objects land on power lines and cause them to produce high-energy flashes of electricity that can start fires. That is why utilities in California and other states have at times shut down power in recent years before strong winds arrive.

The National Weather Service expected winds of up to 45 miles per hour last Tuesday, with gusts of 60 miles per hour — conditions that were amplified by Hurricane Dora, which traveled across the Pacific Ocean about 700 miles to the south.

“We allege that many of the regulatory laws that require maintenance of equipment were broken,” said James Frantz, chief executive of the Frantz Law Group, one of several law firms taking action against Hawaiian Electric. “There’s got to be some accountability.” He said his firm was representing five Lahaina residents who were filing lawsuits in a Hawaiian state court on Monday.

Shares in Hawaiian Electric lost over a third of their value on Monday, a sign that investors feared that the company would have to pay out large sums to settle lawsuits filed by homeowners and businesses, and spend enormous amounts to try to fireproof its operations.

“The issue becomes whether they did everything they could that was reasonable to prevent this incident,” said Shahriar Pourreza, an analyst who covers Hawaiian Electric’s stock for Guggenheim Securities. “Was there gross negligence, was there imprudence?”

Hawaiian Electric, established in 1891, operates on Maui through its subsidiary, Maui Electric, and is tiny compared with the Californian utilities that have paid huge wildfire settlements. Its revenue last year totaled $3.7 billion, compared with $21.7 billion at Pacific Gas and Electric of California. Like most other utilities, Hawaiian Electric operates under the scrutiny of public commissioners who have to approve its spending plans.

At a news conference on Monday, Shelee Kimura, the chief executive of Hawaiian Electric, said the company did not have a shut-off program and contended that cutting the power could have created problems for people using medical equipment that runs on electricity.

She also said turning off the power would have required coordination with emergency workers. “In Lahaina, the electricity powers the pumps that provide the water — and so that was also a critical need during that time,” Ms. Kimura said. “There are choices that need to be made — and all of those factors play into it.”

In Lahaina and other towns in West Maui last week, downed power poles and lines littered the highway, blocking roads in some cases. It was unclear how much of the equipment had been tossed over by the strong gusts of wind and how much of it was damaged by the fire.

Power lines have caused catastrophic wildfires in California in recent years, prompting lawsuits that have led to multibillion-dollar payouts by the state’s utilities. Pacific Gas and Electric filed for bankruptcy in 2019 and agreed to pay $13.5 billion to settle claims relating to destructive wildfires, including the Camp Fire, which destroyed the Northern California town of Paradise and killed 85 people.

The Federal Emergency Management Agency and the Pacific Disaster Center, a firm based in Hawaii that provides disaster-related analysis, said on Saturday that more than 2,000 structures had been damaged or destroyed by the recent fires on Maui. And they estimated that it would cost $5.52 billion to rebuild. Mr. Pourreza, the analyst, said in a research note that there was a scenario in which Hawaiian Electric’s liability from the fire could exceed $4 billion. It had $314 million in cash at the end of June.

Pre-emptive power shutdowns are unpopular, because of how disruptive they can be to individuals and businesses. But wildfire experts say that they are a necessary measure, and, with planning, they can be deployed in such a way that they don’t prevent emergency services from operating during the blackout.

“It keeps people safe,” said Michael Wara, a scholar focused on climate and energy policy at Stanford University.

Lightning strikes have been another common source of ignition for wildfires in the Western United States. While not definitive, satellite-based lightning detectors operated by NASA did not indicate lightning activity on Hawaii last Monday or Tuesday.

Local and state officials have said little about what might have caused the fire that eventually engulfed Lahaina on the afternoon of Aug. 8. Earlier that day, Maui County said it had completely contained a small brush fire that was first reported that morning, but later announced at 4:45 p.m. that “an apparent flareup” had forced the closure of one main road and sudden evacuations.

Data from Whisker Labs, a private company that monitors the electrical grid in cities across the country looking for problems that might spark a home fire, appears to show significant faults — or major incidents — on power lines near where the Tuesday morning blaze is believed to have started.

On the night of Aug. 7 and into the early morning hours, its data showed, power lines began losing voltage, which can happen when vegetation interferes with wires, lines touch power poles or electrical equipment malfunctions.

The company said it had almost 1,000 sensors in Hawaii and about 70 on Maui. A major fault was felt by all sensors on the island, but was strongest near Lahaina, Whisker Labs found.

And it was a full eight seconds, “which is an eternity in electrical grid time,” said Bob Marshall, co-founder and chief executive of Whisker Labs, based in Germantown, Md. “Something on the grid was very unhappy for eight seconds and trying to recover from a shock.”

Hawaiian Electric, through Jim Kelly, a spokesman, declined to comment on Whisker Labs’ data and findings.

Ken Pimlott, the former chief of the California Department of Forestry and Fire Protection, said in an interview on Sunday that the notion that power lines might have started the fire was plausible.

He said the Maui fire recalled the 2017 Tubbs fire in California, which tore through wine country north of San Francisco. That fire was caused by private electrical equipment and quickly spread through communities lined up and down steep slopes. As was the case in West Maui, the Northern California community was on the edge of wild lands, making it more vulnerable.

Hawaii’s attorney general, Anne Lopez, said on Friday that she would be “conducting a comprehensive review of critical decision-making and standing policies leading up to, during, and after the wildfires on Maui and Hawaii islands.”

Mr. Wara, of Stanford, said Hawaiian Electric appeared to have ample time to shut down power. He noted that before the high winds hit, the company took the precaution of turning off reclosers, equipment designed to restart the flow of power after an outage.

Hawaiian Electric in a regulatory filing last year detailed measures aimed at reducing the risk of its equipment causing fires. Among other things, the filing said the company was “hardening” poles to withstand high winds and cutting back vegetation, noting that Lahaina was a priority area.

But such measures can take time to complete and be very expensive. Burying power lines costs $3 million to $5 million per mile, said Mr. Wara, who was a member of a California commission that advised lawmakers after the Camp Fire on how to hold utilities accountable for wildfire costs and risks. Typically, such costs are added to customers’ bills under regulatory rules — and Hawaii’s electricity rates are already by far the highest in the United States, according to the U.S. Energy Information Administration.

“Why did they not do the cheap thing — turn the power off?” Mr. Wara said.

Reporting was contributed by Kellen Browning, John Keefe, Susan C. Beachy and Alain Delaquérière.